<?php

define('BASEPATH', dirname(__FILE__).'/'); // 数据库文件路径，即放置本套数据库操作类的目录路径。加载文件时需要使用，请修改为实际路径
define('DB_CONFIG_PATH', BASEPATH.'DB_config.php'); // 数据库配置文件路径。请修改为实际路径

/**
 * CodeIgniter
 * An open source application development framework for PHP
 * This content is released under the MIT License (MIT)
 * Copyright (c) 2014 - 2015, British Columbia Institute of Technology
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 * @package      CodeIgniter
 * @author       EllisLab Dev Team
 * @copyright    Copyright (c) 2008 - 2014, EllisLab, Inc. (http://ellislab.com/)
 * @copyright    Copyright (c) 2014 - 2015, British Columbia Institute of Technology (http://bcit.ca/)
 * @license      http://opensource.org/licenses/MIT	MIT License
 * @link         http://codeigniter.com
 * @since        Version 1.0.0
 * @filesource
 */
defined('BASEPATH') OR exit('No direct script access allowed');

/**
 * Initialize the database
 * @category    Database
 * @author      EllisLab Dev Team
 * @link        http://codeigniter.com/user_guide/database/
 * @param    string|string[] $params
 * @param    bool            $query_builder_override
 *                Determines if query builder should be used or not
 */
function &DB($params = '', $query_builder_override = NULL){
    // 如果$params参数不是DSN则加载数据库配置文件
    if(is_string($params) && strpos($params, '://') === FALSE){
        // 加载数据库
        if(!file_exists(DB_CONFIG_PATH)){
            exit('数据库配置文件 '.DB_CONFIG_PATH.' 不存在！');
        }
        require DB_CONFIG_PATH;

        if(!isset($db) OR count($db) === 0) exit('数据库配置无效！');
        // 将要启用的数据库配置组
        if($params !== '') $active_group = $params;

        if(!isset($active_group)){
            exit('没有找到数据库配置组名。请确认数据库配置文件内是否有$active_group变量');
        } elseif(!isset($db[ $active_group ])){
            exit('没有找到名为 ' . $active_group . ' 的数据库配置组');
        }

        $params = $db[ $active_group ];
    } elseif(is_string($params)){
        /**
         * Parse the URL from the DSN string
         * Database settings can be passed as discreet
         * parameters or as a data source name in the first
         * parameter. DSNs must have this prototype:
         * $dsn = 'driver://username:password@hostname/database';
         */
        // 解析、转义DSN字符串
        if(($dsn = @parse_url($params)) === FALSE) exit('无效的DSN字符串');

        $params = [
            'dbdriver' => $dsn['scheme'],
            'hostname' => isset($dsn['host']) ? rawurldecode($dsn['host']) : '',
            'port'     => isset($dsn['port']) ? rawurldecode($dsn['port']) : '',
            'username' => isset($dsn['user']) ? rawurldecode($dsn['user']) : '',
            'password' => isset($dsn['pass']) ? rawurldecode($dsn['pass']) : '',
            'database' => isset($dsn['path']) ? rawurldecode(substr($dsn['path'], 1)) : ''
        ];

        // 设置了额外的配置项目？
        if(isset($dsn['query'])){
            parse_str($dsn['query'], $extra);

            foreach($extra as $key => $val){
                if(is_string($val) && in_array(strtoupper($val), ['TRUE', 'FALSE', 'NULL'])){
                    $val = var_export($val, TRUE);
                }

                $params[ $key ] = $val;
            }
        }
    }

    // 没设置数据库驱动？
    if(empty($params['dbdriver'])) exit('必须设置一个数据库驱动(dbdriver)');

    // Load the DB classes. Note: Since the query builder class is optional
    // we need to dynamically create a class that extends proper parent class
    // based on whether we're using the query builder class or not.
    if($query_builder_override !== NULL){
        $query_builder = $query_builder_override;
    }
    // Backwards compatibility work-around for keeping the
    // $active_record config variable working. Should be
    // removed in v3.1
    elseif(!isset($query_builder) && isset($active_record)){
        $query_builder = $active_record;
    }

    require_once(BASEPATH . 'DB_driver.php');

    // 根据是否加载查询构造器($query_builder)来基于不同的父类声明CI_DB类
    if(!isset($query_builder) OR $query_builder === TRUE){
        require_once(BASEPATH . 'DB_query_builder.php');
        if(!class_exists('CI_DB', FALSE)){
            /**
             * CI_DB
             * Acts as an alias for both CI_DB_driver and CI_DB_query_builder.
             * @see    CI_DB_query_builder
             * @see    CI_DB_driver
             */
            class CI_DB extends CI_DB_query_builder{
            }
        }
    } elseif(!class_exists('CI_DB', FALSE)){
        /**
         * @ignore
         */
        class CI_DB extends CI_DB_driver{
        }
    }

    // 加载数据库驱动
    $driver_file = BASEPATH . 'drivers/' . $params['dbdriver'] . '/' . $params['dbdriver'] . '_driver.php';

    file_exists($driver_file) OR exit('没有找到 '.$params['dbdriver'].' 数据库驱动');
    require_once($driver_file);

    // 实例化数据库驱动适配器
    $driver = 'CI_DB_' . $params['dbdriver'] . '_driver';
    $DB = new $driver($params);

    // Check for a subdriver
    // CI 3.0.0 新增的功能
    // 更新记录：Added subdrivers support (currently only used by PDO)
    if(!empty($DB->subdriver)){
        $driver_file = BASEPATH . 'drivers/' . $DB->dbdriver . '/subdrivers/' . $DB->dbdriver . '_' . $DB->subdriver . '_driver.php';

        if(file_exists($driver_file)){
            require_once($driver_file);
            $driver = 'CI_DB_' . $DB->dbdriver . '_' . $DB->subdriver . '_driver';
            $DB = new $driver($params);
        }
    }

    $DB->initialize();
    return $DB;
}

/**
 * PHP版本对比函数。返回当前环境的PHP版本是否高于或等于$version
 * @param $version
 */
function is_php($version){
    return version_compare(PHP_VERSION, $version, '>=');
}

/**
 * 记录日志。CI的数据库类中多处调用此函数。于是声明出来，也方便各位收集日志
 * @param $level 错误等级：'error'、'debug'或'info'
 * @param $message 错误信息
 */
function log_message($level, $message){}